The code is simple Here you go my friend, let ME tell you how to do this. So, you made a valid resource pack with the sounds folder. Now, go to the assets/minecraft folder, and create a .json with this code:

{
"foldername.soundname": {
"sounds": [
"foldername/soundname"
]
}
}

You can create a folder called... MySounds or Music or Songs, replace the foldername in the code with the name of that folder and replace soundname with the name of the sound. NOTE: To make sure this will work, rename your sound to something like mysound1 or sound1 or song1. Never do something like this in a .json: Xtrullor - Nirmiti. Just make sure it doesnt have spaces. To play the sound in minecraft, use the top line in this command, lets say my folder is MySounds and sound is MySound. This is the /playsound: /playsound minecraft:MySounds.MySound master @a ~ ~ ~